Financing Activities - Other Borrowings (Parenthetical) (Detail)	9 Months Ended
	Sep. 30, 2013
Old National Bancorp [Member]
Proforma Debt Instrument [Line Items]
Maturity, Start date	Mar. 01, 2035
Maturity, End date	Jun. 01, 2037
Old National Bancorp [Member] | Junior Subordinated Debt [Member] | Minimum [Member]
Proforma Debt Instrument [Line Items]
Variable rates	1.85%
Old National Bancorp [Member] | Junior Subordinated Debt [Member] | Maximum [Member]
Proforma Debt Instrument [Line Items]
Variable rates	2.00%
Old National Bank [Member]
Proforma Debt Instrument [Line Items]
Maturity, Start date	Oct. 01, 2013
Maturity, End date	Jan. 01, 2023
Old National Bank [Member] | Securities Sold under Agreements to Repurchase [Member]
Proforma Debt Instrument [Line Items]
Maturity, Start date	Jan. 01, 2017
Maturity, End date	Jan. 01, 2018
Old National Bank [Member] | Securities Sold under Agreements to Repurchase [Member] | Minimum [Member]
Proforma Debt Instrument [Line Items]
Fixed rates	2.47%
Old National Bank [Member] | Securities Sold under Agreements to Repurchase [Member] | Maximum [Member]
Proforma Debt Instrument [Line Items]
Fixed rates	2.50%
Old National Bank [Member] | Federal Home Loan Bank Advances [Member] | Minimum [Member]
Proforma Debt Instrument [Line Items]
Variable rates	0.32%
Fixed rates	0.14%
Old National Bank [Member] | Federal Home Loan Bank Advances [Member] | Maximum [Member]
Proforma Debt Instrument [Line Items]
Variable rates	0.36%
Fixed rates	8.34%